1. Field of the Invention
The present invention relates to a magnetic head suspension for supporting a magnetic head slider that reads and/or writes data from and to a recording medium such as a hard disk drive.
2. Related Art
Increase in capacity of a magnetic disk device requires improvement in accuracy for positioning a magnetic head slider on a target track. In this regard, there has been proposed a magnetic head suspension that includes paired piezoelectric elements functioning as a sub actuator and enables micro motion of the magnetic head slider in a seek direction by the paired piezoelectric elements in addition to coarse motion of the magnetic head slider in the seek direction by a main actuator such as a voice coil motor (for example, see Japanese Unexamined Patent Application Publication Nos. 2002-251854, 2009-080915 and 2002-050140, which are hereinafter referred to as prior art documents 1-3, respectively).
More specifically, the magnetic head suspension includes a load bending part that generates a load for pressing the magnetic head slider toward a disk surface, a load beam part that transmits the load to the magnetic head slider, a supporting part that supports the load beam part via the load bending part and is swung about a swing center directly or indirectly by the main actuator, a flexure part that is supported by the load beam part and the supporting part while supporting the magnetic head slider, and the paired piezoelectric elements that is attached to the supporting part.
The supporting part is provided with a proximal end section that is connected directly or indirectly to the main actuator, a distal end section to which the load bending part is connected, an open section that is positioned between the proximal end section and the distal end section in a suspension longitudinal direction, and paired right and left connecting beams that are positioned on both sides of the open section in a suspension width direction and connect the proximal end section and the distal end section.
Each of the paired piezoelectric elements has a piezoelectric main body and paired electrode layers disposed on both sides of the piezoelectric main body in a thickness direction thereof, and expands and contracts in a direction perpendicular to the thickness direction in accordance with application of a predetermined voltage between the paired electrode layers.
In the magnetic head suspension, the paired piezoelectric elements have distal end portions and proximal end portions that are respectively fixed to the distal end section and the proximal end section in a state that they are symmetrical with each other with respect to a suspension longitudinal center line and have expansion and contraction directions different from each other.
In the thus configured magnetic head suspension, the distal end section can be swung in the seek direction with respect to the proximal end section while the paired connecting beams being elastically deformed in accordance with expanding movement of one of the paired piezoelectric elements and contracting movement of the other one of the paired piezoelectric elements. Consequently, the micro motion in the seek direction of the magnetic head slider, which is supported by the distal end section through the load bending part, the load beam part and the flexure part, can be performed.
However, each of the magnetic head suspensions disclosed in the prior art documents 1-3 has a problem that the paired piezoelectric elements are likely to be deformed in a bending manner in the thickness direction when being expanded and contracted.
If the paired piezoelectric elements are deformed in a bending manner upon the expansion and contraction thereof, the distal end section is twisted with respect to the proximal end section. As a result, floating movement of the magnetic head slider is become unstable when it is moved in the seek direction.
First, the problem will be explained in detail in case of the magnetic head suspensions disclosed in the prior art documents 1 and 2.
In each of the magnetic head suspensions disclosed in the prior art documents 1 and 2, the distal end section of the supporting part is formed with a distal-end-side cutaway portion that is opened in the upward direction as well as in a direction towards the open section, and the proximal end section is formed with a proximal-end-side cutaway portion that is opened in the upward direction as well as in a direction towards the open section.
The distal-end-side cutaway portion includes a distal-end-side vertical surface that faces towards the proximal side in the suspension longitudinal direction and a distal-end-side horizontal surface that extends from a lower edge of the distal-end-side vertical surface towards the proximal side in the suspension longitudinal direction to be opened into the open section.
The proximal-end-side cutaway portion includes a proximal-end-side vertical surface that faces towards the distal side in the suspension longitudinal direction and a proximal-end-side horizontal surface that extends from a lower edge of the proximal-end-side vertical surface towards the distal side in the suspension longitudinal direction to be opened into the open section.
Each of the paired piezoelectric elements is fixed to the supporting part by insulative adhesive agents that are disposed between its distal-side end surface and the distal-end-side vertical surface, between a distal side of a lower electrode layer that is positioned on the lower side and the distal-end-side horizontal surface, between its proximal-side end surface and the proximal-end-side vertical surface, and between a proximal side of the lower electrode layer and the proximal-end-side horizontal surface, respectively.
That is, in each of the magnetic head suspensions disclosed in the prior art documents 1 and 2, the lower electrode layer of each of the paired piezoelectric elements has the distal side and the proximal side that are fixed to and retained by the distal-end-side horizontal surface and the proximal-end-side horizontal surface with the insulative adhesive agents, respectively, in a state where the distal side and the proximal side face the distal-end-side horizontal surface and the proximal-end-side horizontal surface, respectively. On the other hand, an upper electrode layer of the each of the paired piezoelectric elements that is positioned on the upper side (on the side opposite to the disk surface) is in a substantial free state with respect to the supporting part.
Accordingly, when the piezoelectric element is expanded or contracted in the suspension longitudinal direction upon application of the predetermined voltage between the paired electrode layers (the upper and lower electrode layers) of the piezoelectric element, the lower electrode layer whose distal side and proximal side are faced and fixed to the distal-end-side horizontal surface and the proximal-end-side horizontal surface respectively is restricted in the expansion and contraction movement while the upper electrode layer can be expanded or contracted freely.
As a result, the piezoelectric element is deformed in a bending manner in the direction orthogonal to the disk surface when being expanded or contracted, whereby floating movement of the magnetic head slider is become unstable when it is moved in the seek direction by the piezoelectric elements.
Next, the problem will be explained in detail in case of the magnetic head suspension disclosed in the prior art document 3.
In the magnetic head suspension disclosed in the prior art document 3, the supporting part is provided with a distal-end-side plate fixed to a lower surface (a surface facing the disk surface) of the distal end section so as to be at least partially positioned within the open section in plan view, and a proximal-end-side plate fixed to a lower surface of the proximal end section so as to be at least partially positioned within the open section in plan view.
Each of the paired piezoelectric elements is fixed to the supporting part by insulative adhesive agents that are disposed between its distal-side end surface and a wall surface of the distal end section, between the distal side of the lower electrode layer and the distal-end-side plate, between its proximal-side end surface and a wall surface of the proximal end section, and between the proximal side of the lower electrode layer and the proximal-end-side plate, respectively.
That is, in the magnetic head suspension disclosed in the prior art document 3, the lower electrode layer has the distal side and the proximal side that are fixed to and retained by the distal-end-side plate and the proximal-end-side plate with the insulative adhesive agents, respectively, in a state where the distal side and the proximal side face the distal-end-side plate and the proximal-end-side plate, respectively. On the other hand, the upper electrode layer is in a substantial free state with respect to the supporting part.
Accordingly, also in the magnetic head suspension disclosed in the prior art document 3 in the same manner as the magnetic head suspensions disclosed in the prior art documents 1 and 2, the piezoelectric elements are deformed in a bending manner in the direction orthogonal to the disk surface when being expanded or contracted, whereby floating movement of the magnetic head slider is become unstable when it is moved in the seek direction by the piezoelectric elements.